neptune

any whelk of the genus Neptunea, especially N. decemcostata, common along the eastern coast of North America and having a shell with seven to ten raised reddish-brown spiral ridges on a pale beige or yellow background.

Neptune

[nep-toon, -tyoon] /ˈnɛp tun, -tyun/

noun

1.

the ancient Roman god of the sea, identified with the Greek god Poseidon.

2.

the sea or ocean:

Neptune's mighty roar.

3.

Astronomy. the planet eighth in order from the sun, having an equatorial diameter of 30,200 miles (48,600 km), a mean distance from the sun of 2794.4 million miles (4497.1 million km), a period of revolution of 164.81 years, and two moons.

Neptune1

/ˈnɛptjuːn/

noun

1.

the Roman god of the sea Greek counterpart Poseidon

Neptune2

/ˈnɛptjuːn/

noun

1.

the eighth planet from the sun, having fourteen known satellites, the largest being Triton and Nereid, and a faint planar system of rings or ring fragments. Mean distance from sun: 4497 million km; period of revolution around sun: 164.8 years; period of rotation: 14 to 16 hours; diameter and mass: 4.0 and 17.2 times that of earth respectively

Neptune

late 14c., "god of the sea," from Latin Neptunus, son of Saturn, brother of Jupiter, the Roman god of the sea (later identified with Greek Poseidon), probably from PIE root *nebh- "cloud" (cf. Latin nebula "fog, mist, cloud;" see nebula), via a sense of "moist, wet." The planet so named was discovered by Galle in 1846. Until the identification of Pluto in 1930, it was the most distant planet known.

(něp'tn') The eighth planet from the Sun and the fourth largest, with a diameter almost four times that of Earth. Neptune is a gas giant with a very active weather system, exhibiting extremely long and powerful storms with the fastest winds observed in the solar system. Neptune's axis is tilted 28.8° from the plane of its orbit, and its summer and winter seasons each last 40 years. For a period of 20 years out of every 248, Pluto's highly elliptical orbit crosses within that of Neptune, making Neptune the farthest planet from the Sun during that period. Neptune has four faint rings and 13 known moons and appears blue due to the absorption of red light by the methane within its atmosphere. See Table at solar system.

Note: Neptune is frequently portrayed as a bearded giant with a fish's scaly tail, holding a large three-pronged spear, or trident.

Note: The eighth planet from the sun (the Earth is third) is named Neptune.

Neptune definition

In astronomy, a major planet, the eighth planet from the sun. Neptune is named for the Roman god of the sea. Neptune is similar in size and composition to Uranus. It is usually visible only through a telescope and was discovered in the 1840s. For a period ending in 1999, Pluto's orbit took it inside the orbit of neptune. (Seesolar system; see under “Mythology and Folklore.”)

Note: Some astronomers have suggested that Pluto is not a planet in the usual sense but is an object more like an asteroid, and that Neptune, therefore, is actually the outermost planet.